And st



reamed Apr. 10, 1925.

1 UNITEDSTATES PATENT OFFICE- Isnnonn raoonsorrnor CHICAGO, rnrirnors, AND s'ritna trnuscocr'r, or

BIRMINGHAM, 01110.

. .arncnarr oovnnrne.

INo Drawing.

Tl'llSdIlVBIllilOll relates to improvements in flexible gas retaining fabrics for aircraft and more particularly to the gas retaining fabric usedjin the gas cells of aircraft of the Zeppelin type. i

' in parts hereinafter pointed out.

-The disadvantages of a gas retaining fabric using goldl'ieaters skin as an impermeable film has been described in our pending specification filed Apr. 11, 1925, Serial No. 22346 fora fabric using cellulose or sheet viscose as a substitute for "the goldbeaters skin. The fabric described hereafter is intended to overcome the disrulvantageiti incident to the preparation of goldbeaters skin fabric in another manner.

It has been found that a film produced from a mixture of viscose and latex has a very high resistance to the passage-of gases. Eluch material can be produced. either in large sheets or spread directly on cloth in a manner similar to that in which rubber is applied. We have prepared and tested many samples of fabric using this film prepared from the mixture of latex and viscose and found them to be satisfactory for this purpose.

A fabric treated with our invention is not only impermeable to gases but also is extremely flexible, being equally as pliable as goldbeaters skin and therefore is particularly adapted for the purpose designed.

The following example will illustrate the method of preparing gas impermeable fabrics from a mixture of viscose and latex. Dissolve 0.29 gins. of tetramethyl thiuram disulfide in cc. of acetone. Add this solutionquickly to 400 cc. of water at C. This is immediately followed by the addition, with vigorous agitation, of 70 gms. of rubber latex containing 40% of solid matter. It is essential that this operation be very quickly carried out in order to prevent the coagulation of the first substance added.

Application filed April 11, 1825. Serial No. 22,347.

Three gms. of zinc sulphate, dissolved in 10cc. of water, are treated with 7 cc. of ammonia water containing 29% of ammonia. The white precipitate which is formed at first should be completely redissolved be fore proceeding further. This solutionis then added to the latex solution above, agit-ating well. Two hundred and fifty gins. of viscose are then added to this mixture and stirred well until a homogeneous solution results. The viscose usedcmust not have aged excessively at the time of use. Swollen fibrous particles will separate from a mixture ofold viscose and latex. The length of time such viscose solutions may be kept without excessive deterioration depends upon the temperature at which they are kept, decomposition occurring more rapidly at higher temperatures. -We have found it possible, however, touse viscose which had been stored in a glass, vessel kept in anice chest for as long as 1520 days. The viscose-latex mixtureprepared by. the above method should be kept at a temperature not exceeding 20 C. until applied.

In order to prepare a gas impermeable flexible fabric from the viscose-latex mixture, the fabric is first sized with a suitable gelatine or glue adhesive for the viscoselatex film that is later built upon it. The viscose-latex mixture, prepared as outlined above, is then spread upon the sized fabric, a total of eight to fifteen coats being spread, depending upon the impermeability and weight desired. Each coat is dried by passinga current of air at a temperature of 40 C. over its surface before the application of the next coat. When the last coat is dry, the fabric is passed through a bath composed of an aqueous solution containing mag nesium sulphate at a temperature of C. The duration of this procedure depends upon the exact temperature used, the fabric being left in this bath until it acquires a uniform tan color. It is then passed through a bath containing a 2% aqueous solution of sodium bisulphite until it becomes white in color. After this it is washed with cold water to remove water soluble salts and passed through a bath containing 15% of glycerine by volume. The fabric is then allowed to drain and dry. The fabric thus obtained is light in weight and virtually impermeable to gases. After standing for several Weeks, it acquires greater strengthand becomes sufficiently flexible to Withstand wrinkling Without any noticeable increase in permeability.

Itmust be understood that We do not limit ourselves to the use of proportions of the various ingredients specified in the above example. Furthermore, We do not limit ourselvesto the use of the accele'ator, tetramethyl thiuram disulphide, or the use of the activator, zinc sulphate, or the temperatures specified in this example. WVe reserve also the right to change the order in which the various ingredients may be added in preparingthe viscose-latex mixture.

1 It Will thus be seen that the present invention'provides. a simple and practical flexible gas retaining fabric for use on aircraft adapted to accomplish, among others. all of the objects and advantages herein set forth.

. magnesium sulphate then through a bath of sodium bisulphite, then of clear water, and finally of glycerlne, to convert the film of viscose-latex into one of cellulose-rubber and to render the coating insoluble in water and to render it flexible.

2. A method of rendering a fabric impermeable to gases and flexible consisting in applying an adhesive to said fabric, applying thereupon a plurality of layers of viscose-rubber latex solution drying each layer before applying the next, and passing the finally drici'l coated fabric first through a bath of magnesium sulphate then through a bath of sodium bisulphite, then of clear water, and finally of. glycerine, to convert the lilm of viscose-latex into one of celluloserubber'and to render the coating insoluble in Water and to render it flexible.

3. A method of treating a fabric to render the same flexible and impermeable to gases consisting in applying an adhesive to the fabric, superimposing thereupon a plurality of layers of viscose-rubber latex solution, drying each layer before applyin the next. bathing the finally dried coated fabric in a solution of magnesium sulphate, bathing in a solution. of sodium bisulphite, removing soluble salts therefrom, passing it through a bath containing glycerine, draining and drying.

l. A fabric coated with gelatine having a viscose-rubber latex superimposed thereupon and treated with a plasticizing agent, where by the fabric is rendered flexible and impel-.- ineable to gases.

Signed at \Vashington, District of 00111111 bia, this 9th day of January, 1925.

ISADORE M. JACOBSOHN. STARR TRUSCOTT.

(ill 

